The instant invention relates generally to composite material machinery seals disposed in grooves or seal glands to provide a fluid seal between relatively moving machinery parts. Specifically, the invention comprises a seal element having a relatively large central mass, static and dynamic sealing lips thereon, and an axial vented element to provide superior sealing characteristics while preventing fluid pressure build-up between seal stages in multiple seal systems.
U-rings are known-in-the art seals for pistons or rods, or any axially displaceable machine part moveable through an annular passage in a complementary part. They provide a fluid barrier between reciprocating piston rods or pistons and a fluid under pressure by means of a dynamic sealing lip that bears against a rod shaft or a piston wall.
In high pressure fluid system applications, for example hydraulic systems for heavy machinery, it is well known in the art to use a plurality of U-ring seal assemblies arranged in series along the axis of a shaft or piston to prevent high pressure fluid from leaking past the seals. The upstream seals in these multi-seal arrangements are known as buffer seals. They serve to protect the primary rod or piston seal from high-pressure surges, thereby extending the useful life thereof.
However, the aforementioned serial arrangement of seal assemblies in high-pressure applications suffers from several disadvantages. Buffer seals must release any pressure that may exist in the area between the primary seal and the buffer seal or seals when that pressure exceeds system fluid pressure. Conventional U-ring seals are often made from flexible material that tends to rotate in the seal gland (or groove) thereby causing the static sealing lip thereof to contact an axial wall of the seal gland. This rotation and the subsequent contact of the seal assembly with the axial wall of the seal groove results in failure of the seal to release the pressure build-up between seal stages. The pressure build-up can become substantially greater than system fluid pressure, thereby causing damage to the primary system seals and poor cylinder efficiency.